The present invention relates to a process for sealing a seam of a polyurethane/geotextile composite applied over concrete or earthen canals and/or ditches with a non-sagging polyurethane composition. The present invention also relates to a process for patching a polyurethane/geotextile composite with a non-sagging polyurethane composition. The present invention further relates to a process for repairing concrete canals and/or ditches with a non-sagging polyurethane composition. The present invention also relates to a ditch and/or canal lined with a polyurethane/geotextile composite wherein the integrity of the canal and/or ditch has been maintained with a non-sagging polyurethane composition.
In recent years, the management of natural resources has become important in many countries throughout the world. Efforts have been directed both toward the conservation of our resources and toward the elimination of pollution from our environment. Particular emphasis has been placed on waste leakage and water loss.
Losses in the distribution of water using unlined irrigation ditches are estimated at a minimum to be 25% and in some situations to be more than 50% depending upon the porosity of the ditch surface and the distance the water is being moved. In most rural areas, ditches are formed by excavating the soil to the desired depth and width. The water moves through the ditch in contact with the exposed natural surface. This can be sand, clay, rocks, etc. and, more commonly, mixtures thereof. The porosity will depend upon the proportions of the different components.
The loss of water in unlined irrigation ditches was at one time considered acceptable only because the supply of water exceeded demand. However, as civilization has developed and world population increased, more water is required for both greater food production and for markedly increasing non-agriculture uses. In addition to greater domestic uses in sanitation, industry now employs large quantities of water in manufacturing and processing procedures.
This high level of consumption plus the very high cost of developing new water supplies has shifted attention to water conservation. Domestic appliances that use less water have been developed. Also, industry has installed recycling purification systems to reduce water consumption.
Although conservation efforts have reduced water consumption to a degree, water is still in relatively short supply, particularly in recent years with the severe droughts in the United States and other countries. Since the most cost effective conservation opportunities and readily accessible water supplies already have been developed, greater attention must be directed to improving the efficiency of water distribution systems.
Improvements in water distribution have been made. A limited number of ditches and canals have been lined with concrete and/or preformed concrete pipes. Concrete is durable and has a long life when properly used. However, concrete is expensive to place and finish and is damaged by unfavorable temperatures during curing. Also, concrete is subject to frost damage, cracking and heaving which results in leaks.
Processes for forming composite liners for canals and ditches and apparatus to perform such a processes are disclosed, for example, in U.S. Pat. Nos. 4,872,784; 4,955,759; 4,955,760; 5,049,006; 5,062,740; 5,421,677; 5,607,998; and 5,639,331.
U.S. Pat. No. 5,421,677 (xe2x80x9cthe ""677 patentxe2x80x9d) is directed to an improved process of forming a ditch liner. The process of the ""677 patent discloses the use of a mixture comprising one or more polyisocyanates, a polyol mixture, one or more fillers, and a catalyst. The mixture of the ""677 patent is dispensed on a geotextile, thereby forming a liquid polyurethane soaked geotextile composite. The liquid polyurethane soaked geotextile composite is then placed over the surface of an area to be lined and allowed to cure, thereby forming a polyurethane/geotextile composite. The polyurethane/geotextile composite must be cut to be placed over obstructions in the area to be lined. In a canal, for example, obstructions such as valves and gates are present. When the polyurethane/geotextile composite is cut around these obstructions, a seam is generated between the surface of the area being lined and the polyurethane/geotextile composite. This seam must be sealed in order to obtain a watertight connection between the area being lined and the polyurethane/geotextile composite.
A non-sagging polyurethane composition is specifically well suited to be used as a seam sealant because it can be applied to seams as a bead, which subsequently can be spread over the seam using, for example, a spatula. A non-sagging polyurethane composition would exhibit excellent adhesion to the concrete of the ditch and/or canal as well as to the polyurethane/geotextile composite and, after curing, provide a watertight seal. The same non-sagging composition could be used to fill tears, rips and/or other abrasions in the polyurethane/geotextile composite. Additionally, the same non-sagging composition could be used to fill holes and cracks in the concrete or to consolidate loose pieces of concrete prior to the application of the polyurethane/geotextile composite.
Various non-sagging polyurethane compositions are known in the art and described in, for example, in U.S. Pat. Nos. 4,444,976; 4,552,934; 4,698,408; 4,728,710; 4,743,672; 4,954,199; 4,994,540; 5,059,672; 5,164,473; and 5,166,303.
These patents disclose two-component polyurethanes basically consisting of a polyisocyanate or polyisocyanate prepolymer component, and a curative component containing a polyol and a polyamine.
U.S. Pat. No. 4,444,976 (xe2x80x9cthe ""976 patentxe2x80x9d) discloses sag-resistant adhesive two component compositions. These compositions require an isocyanate prepolymer, a low molecular weight polyol containing at least 2-5 hydroxyl groups and a secondary diamine having a molecular weight of up to about 325. The adhesive claimed in the ""976 patent exhibits a gel time at 24xc2x0 C. of at least two minutes. The relatively short gel time of the adhesive claimed in the ""976 patent makes it unsuitable for outdoor applications where gel times of more than 10 minutes are usually required.
U.S. Pat. No. 5,607,998 (xe2x80x9cthe ""998 patentxe2x80x9d) also discloses non-sagging polyurethane compositions. These compositions require a liquid polyisocyanate, a liquid isocyanate-reactive mixture, one or more hydroxyl group containing compounds, one or more diamines, polyamines, amine terminated polyethers and mixtures thereof, with at least one of the organic compounds containing at least one aromatic amine group, and one or more low molecular weight diols or triols, and an inorganic filler mixture composed of glass flakes and talc. The addition of talc to glass flakes containing liquid polyurethane raw materials provides homogeneous, phase stable systems. The reaction mixture as described in the ""998 patent forms a non-sagging polyurethane composition, which is sandable once it is fully cured. The use of two fillers, one being an extremely abrasive glass filler, is a disadvantage in applications where sandability is unnecessary.
Whenever a ditchliner is installed according to the ""677 patent, the geotextile sheets soaked with the liquid solidifiable polyurethane are applied in such a fashion that the sheets overlap to a certain extent in order to obtain a seamless liner after the resin has cured. Due to the unevenness in dirt and broken concrete ditches, wrinkles are often formed at the seam of the overlapping portion resulting in openings and potential leakage. This is a problem that has to be addressed to provide a functioning liner for canals and ditches.
In the case of large wrinkles in the polyurethane geotextile composite, insufficient adhesion to the surface is obtained and water may seep behind the liner, and possibly result in separation of the liner from the substrate. In those cases the wrinkles are preferably cut open. The liner then has to be adjusted to the surface and the newly generated seam has to be sealed.
Canals and ditches have slidegate turnouts to direct the waterflow into other ditches or to irrigate fields by flooding. The polyurethane geotextile composite liner has to be cut around these outlets and the seams between the ditch surface and the liner have to be sealed to avoid water penetration behind the liner. To solve the above-mentioned problems a seam sealant has to be applied.
In canals and ditches that are already lined, damage can occur to the liner in the form of rips, tears, and/or other abrasions to the liner, which have to be repaired for the liner to be fully functional again.
In concrete canals and ditches where leakage is occurs through cracked and broken concrete, it is often desirable to patch, consolidate, and repair cracked and broken concrete as such, or prior to the application of a new liner.
For the foregoing reasons, it would be desirable to develop a non-sagging polyurethane composition, which can be used as a seam sealant for a polyurethane/geotextile composite. It would also be desirable to use the same composition as a non-sagging polyurethane composition to repair rips, tears and/or other abrasions on a polyurethane/geotextile composite. Finally, it would also be desirable to use such a non-sagging polyurethane composition for repairing broken and/or loose concrete in canals and/or ditches.
It is an object of the present invention to provide a process for sealing a seam of a polyurethane/geotextile composite installed in a ditch and/or canal.
It is another object of the present invention to provide a process for patching a polyurethane/geotextile composite installed in a canal and/or ditch.
It is a further object of the present invention to provide a process for repairing loose and/or damaged concrete in a canal and/or ditch.
It is also an object of the present invention to provide a ditch and/or canal lined with a polyurethane/geotextile composite wherein the integrity of the canal and/or ditch has been maintained with a non-sagging polyurethane composition.
These and other objects, which will be apparent to those skilled in the art, are accomplished by dispensing a non-sagging polyurethane composition onto an area to be sealed, repaired, and/or patched, the non-sagging polyurethane composition being a reaction product of: a) a liquid polyisocyanate component; b) about 80-98% by weight, based on the total weight of b) and c), of a liquid isocyanate reactive component comprising one or more hydroxyl group containing compounds having from about 2 to about 6 hydroxyl groups and a number average molecular weight of from at least 250 to about 8,000, and, optionally, one or more low molecular weight diols or triols having hydroxy equivalent weights of from about 31 to 99; c) from about 2-20% by weight, based on the total weight of b) and c), of an isocyanate-reactive compound containing at least two amine groups; optionally, d) one or more fillers; and, optionally, e) a catalyst.